ANALYSIS

China’s recent announcement that it would increase defense spending by 12.2 percent in 2014 is making some American allies nervous in a region where perception matters and the possible flashpoints are numerous.

President Barack Obama will leave Tuesday for a four-nation trip to Asia, looking to recharge a focus on the region, an ambitious initiative that’s been sidetracked by domestic politics and international conflicts elsewhere.

BEIJING — In a fresh reminder of the unresolved wartime grievances between China and Japan, authorities in Shanghai have seized a Japanese ship over claims dating back to the 1930s.

Mitsui O.S.K. Lines said Monday that one of its iron ore carriers, the Baosteel Emotion, was impounded Saturday. Japan’s top government spokesman, Yoshihide Suga, denounced the move, saying it could have a “chilling effect” on all Japanese companies doing business in China. “We are deeply apprehensive,” he added.

Tensions between Tokyo and Beijing have been on the rise. Japan is worried about China’s increasing military might, while China is nervous about efforts in Japan to revise its post-World War II pacifist constitution.

The two countries are sparring over a group of uninhabited islands, and Japanese Prime Minister Shinzo Abe’s December visit to the Yasukuni shrine in Tokyo that critics say honors war criminals has drawn strong fire from Beijing. Abe on Monday sent a ritual offering to the shrine to mark the start of the spring festival.

Nevertheless, the extensive economic ties between the two neighbors have been seen as a steadying influence, and the seizure of the ship appeared to be the first case of a Chinese court confiscating Japanese assets related to wartime claims.

According to the Shanghai Maritime Court, the Baosteel Emotion was impounded because Mitsui O.S.K. Lines has failed to pay a Chinese company, the Chung Wei Steamship Co., about $28 million as ordered by Chinese courts in 2010.

According to a timeline of the dispute released Monday by Mitsui O.S.K. Lines, in 1936, a Japanese company called Daido Kaiun — a predecessor to Mitsui O.S.K. Lines — chartered two ships from Chung Wei Steamship Co. They were later expropriated by the Japanese government and sank or were lost at sea during the Sino-Japanese war.

Heirs to the owner of Chung Wei sought multiple times to pursue damages and reparations in Japanese courts in the 1970s, to no avail. Japan says all such grievances were settled under an agreement in 1972, when the two countries normalized relations.

In 1988, however, the heirs filed a case with the Shanghai Maritime Court. Finally, in 2007, the court ruled in their favor, ordering Mitsui O.S.K. Lines to pay $28 million. The Japanese firm tried to appeal the ruling with several Chinese courts to no avail, and later attempted to negotiate a settlement.

In December, the plaintiffs asked Chinese authorities to enforce a confiscation order, and officials acted this month after the Baosteel Emotion docked near Shanghai.

Ironically, the ship was carrying iron ore from Australia on behalf of another Chinese company, Baoshan Iron and Steel, which has a 25-year contract with Mitsui-O.S.K. Lines for transport of the raw material to China.